The dynamical properties of six SDSS quasar pairs at z \leq 0.8 are investigated .
The pairs have proper transverse separation R _ { \perp } \leq 500 kpc , and velocity difference along the line of sight \Delta V _ { r } \leq 500 km/s .
If they are bound systems their dynamical mass can be evaluated and compared with that of host galaxies .
Evidence is found of an excess of the former mass with respect to the latter .
This suggests that these quasar pairs are hosted by galaxies with massive dark halos or that they reside in a group/cluster of galaxies .